This invention relates to a system for positioning a photosensitive media sheet on an exposure platen in registration with a given datum from which datum a scanning operation is conducted on the media sheet and deals more particularly with a media handling system wherein conformable media is capable of being handled from a supply of such media in flat form and configured by the system to take the shape of the drum support surface and further deals with an improvement in laser scanners wherein motion controls of the spinner assembly are directly dependent upon the desired print resolution of the image.
Exposing of media by scanning is made more efficient through the use of drum plotters which employ a rapidly spinning projection mirror which directs a light beam from a laser source downwardly onto the photosensitive material which is supported on the drum support surface. Media which is supported on the drum surface must be flexible enough to conform to the arcuate contour of this surface, but made of a strong enough material to be used, for example, directly in a lithographic printing press. Media consists of a photographically sensitive coating, e.g. emulsion, on a base material of polyester or aluminum. Such media sheets are usually provided in a supply of such sheets layered onto each other in a flat orientation and contained in a cassette. As such, any handling device which is used to automatically load the media sheets into drum plotters must be capable of handling a somewhat mechanically unstable element between this supply station and the scanning station, and thereafter to any subsequent handling station, such as one wherein the media is developed.
Media of the type of which the present invention is concerned has a photosensitive layer or emulsion formed on it which is sensitive to radiant energy in a given wavelength to expose areas of the emulsion where a positive or negative image is to be made. In some instances, the emulsion used is sensitive to room light, and it is therefore necessary that loading and scanning operations be done in "dark rooms". Operating in dark rooms is not advantageous from a production standpoint because the workers involved in the handling process must operate in a dimly light room, usually under red light and must always be conscious about the exposure of media to stray room light, such as when a door opens.
Accordingly, it is an object of the invention to provide a media handling system whereby media is taken from a supply of media loaded into the system in a light-tight condition and is thereafter scanned within the light-tight confines of a scanning apparatus.
It is yet a further object of the invention to provide a media handling device for a plotter wherein the media handled is one which is flexible and the handling device is capable of picking and placing an individual media sheet and conforming it to a given configuration so that it can be supported on the partial cylindric support surface of a drum plotter.
Still a further object of the invention is to provide a highly accurate scanning system which is capable of scanning on a media sheet with different pixel densities and light spot diameters in accordance with graphic information inputted as code into the plotter.
Yet a further object of the invention is to provide a scanner in which vibrations otherwise acting on the scanner components are insulated therefrom by structure which negates the effects of such vibrations.
Still a further object of the invention is to provide a scanner of the aforementioned type wherein scan speed and spinner axis axial movement are related to the maximum resolution capabilities of the system.